Diversity, palaeoecology and systematics of a marine fossil assemblage from the Late Triassic Cassian Formation at Settsass Scharte, N Italy

Nützel, Alexander; Kaim, Andrzej

doi:10.1007/s12542-013-0205-1

Cited by 25 publications

(40 citation statements)

References 21 publications

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“…Most larval shells of heterobranchs are smooth. However, there are exceptions such as larval shells of the Triassic–Jurassic families Tofanellidae with pronounced axial ribs (Bandel ; Nützel and Kaim ; Fig. A) or Mathildidae (Gründel and Nützel ).…”

Section: The Gastropod Protoconchmentioning

confidence: 99%

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Larval ecology and morphology in fossil gastropods

Nützel

2014

Palaeontology

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The shell of marine gastropods conserves and reflects early ontogeny, including embryonic and larval stages, to a high degree when compared with other marine invertebrates. Planktotrophic larval development is indicated by a small embryonic shell (size is also related to systematic placement) with little yolk followed by a multiwhorled shell formed by a free‐swimming veliger larva. Basal gastropod clades (e.g. Vetigastropoda) lack planktotrophic larval development. The great majority of Late Palaeozoic and Mesozoic ‘derived’ marine gastropods (Neritimorpha, Caenogastropoda and Heterobranchia) with known protoconch had planktotrophic larval development. Dimensions of internal moulds of protoconchs suggest that planktotrophic larval development was largely absent in the Cambrian and evolved at the Cambrian–Ordovician transition, mainly due to increasing benthic predation. The evolution of planktotrophic larval development offered advantages and opportunities such as more effective dispersal, enhanced gene flow between populations and prevention of inbreeding. Early gastropod larval shells were openly coiled and weakly sculptured. During the Mid‐ and Late Palaeozoic, modern tightly coiled larval shells (commonly with strong sculpture) evolved due to increasing predation pressure in the plankton. The presence of numerous Late Palaeozoic and Triassic gastropod species with planktotrophic larval development suggests sufficient primary production although direct evidence for phytoplankton is scarce in this period. Contrary to previous suggestions, it seems unlikely that the end‐Permian mass extinction selected against species with planktotrophic larval development. The molluscan classes with highest species diversity (Gastropoda and Bivalvia) are those which may have planktotrophic larval development. Extremely high diversity in such groups as Caenogastropoda or eulamellibranch bivalves is the result of high phylogenetic activity and is associated with the presence of planktotrophic veliger larvae in many members of these groups, although causality has not been shown yet. A new gastropod species and genus, Anachronistella peterwagneri, is described from the Late Triassic Cassian Formation; it is the first known Triassic gastropod with an openly coiled larval shell.

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Section: The Gastropod Protoconchmentioning

confidence: 99%

“…A–B, Late Triassic Cassian Formation, northern Italy. A, mathildoid (tofanellid) heterostrophic coaxial larval shell with strong axial ornament; from Nützel and Kaim (). B, tubiferid (‘opisthobranch’) Sinuarbullina sp.…”

Section: The Gastropod Protoconchmentioning

confidence: 99%

Larval ecology and morphology in fossil gastropods

Nützel

2014

Palaeontology

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“…However, the presence of many clearly post-larval, mostly juvenile gastropods suggests that oxygen concentration were sufficient to permit at least temporarily a short live span on the bottom. The tiny gastropod shells reported from the Smithian of north-eastern Vietnam by Kaim et al (2014) have also been interpreted as isolated larval conchs or early juveniles of taxa having mostly planktotrophic larval development. This assumption was based on the small size of the specimens (smaller than 1 mm) and the fact that the initial whorl is present in most specimens showing that the apical portions of gastropods are present (as in the case of the gastropods studied here).…”

Section: Discussionmentioning

confidence: 99%

“…Good protoconch preservation in Early Triassic gastropods has only been reported from the Smithian Sinbad Limestone of Utah, USA (Batten & Stokes 1986, Nützel 2005, Nützel & Schulbert 2005, the Chinese Dayie Formation (Hua Zhang et al 2003), the Early Triassic of Far East Russia (Kaim 2009), the Olenekian of Vietnam (Kaim et al 2014) and from a silicified Griesbachian fauna from Spitsbergen (Foster et al 2017). The total number of described Early Triassic gastropod species is very low and most species are based on poorly preserved material lacking protoconch preservation.…”

Section: Discussionmentioning

confidence: 99%

An Early Triassic (Dienerian) microgastropod assemblage from the Salt Range, Pakistan and its implication for gastropod recovery from the end-Permian mass extinction

et al. 2018

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“…Fürsich & Wendt ; Nützel et al . ; Hagdorn ; Nützel & Kaim ). Among reef builders, calcareous sponges and scleractinian corals are diverse and abundant at some of the fossil sites (Fürsich & Wendt ).…”

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Diversity and palaeoecology of a highly diverse Late Triassic marine biota from the Cassian Formation of north Italy

Hausmann

Nützel

2015

LET

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A sample of marine invertebrates from the Late Triassic Cassian Formation (north Italy) yielded one of the most diverse Early Mesozoic fossil assemblages ever reported (c. 170 species). The assemblage was found in basin clays, but was transported from nearby carbonate platforms as indicated by fragmentation, microbial encrustation and the presence of coated grains and ooids. Most of the specimens are small (< 1 cm) reflecting both, small adult sizes and size sorting during transport. Rarefaction analysis suggests that diversity of surface collection and bulk sampling is the same. However, rank abundance, species richness and taxonomic composition differ strongly according to sampling method. Low‐grade lithification of the sediments is the main reason that high diversity can be recognized, because it facilitates disaggregation and finding of small molluscs. Sample standardization shows that the studied assemblage is much more diverse than known Early Triassic assemblages. However, its diversity is similar to that of Anisian assemblages. This suggests that recovery from the end‐Permian mass‐extinction was quite advanced in the Middle Triassic and alpha‐diversity remained high until the Late Triassic. According to current models, Early Triassic and Anisian faunas match the niche overlap phase of recovery during which diversity is built up by increasing alpha‐diversity, whereas beta‐diversity rises slowly. Subsequently, habitat width of species contracts because of increasing competition, making beta‐diversity the principal drive of overall diversity increase. The diversity pattern of various Late Triassic Cassian associations meets the predictions for the transition from the niche overlap to the habitat contraction phase.: Triassic, Cassian Formation, palaeoecology, diversity, mollusc dominance.

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Diversity, palaeoecology and systematics of a marine fossil assemblage from the Late Triassic Cassian Formation at Settsass Scharte, N Italy

Cited by 25 publications

References 21 publications

Larval ecology and morphology in fossil gastropods

Larval ecology and morphology in fossil gastropods

An Early Triassic (Dienerian) microgastropod assemblage from the Salt Range, Pakistan and its implication for gastropod recovery from the end-Permian mass extinction

Diversity and palaeoecology of a highly diverse Late Triassic marine biota from the Cassian Formation of north Italy

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